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LP-AM243: R5F: "Undefined Instruction" Exception caused by instruction "msr cpsr register"

Tai-Phan Vuong
Prodigy 40 points
Part Number: LP-AM243
Other Parts Discussed in Thread: SYSCONFIG

Hello TI-Support Team,

this is not really a TI specific question, it is referred to the ARM core R5F in general...I still hope you can give me a hint about the fault anyhow.

Based to an example for the LaunchPad AM243x I currently try to rebuild the FreeRTOS library and face with an exception which I really don´t understand:

An "Undefined Instruction" exception is occurred after the assembler instruction "msr cpsr, r12" is executed, please refer to the screenshot below:  

As you can see the register CPSR (= 0x019F), the core is being in "System" mode, respectively privileged mode before executing the instruction.

Due to the Technical Ref of Cortex-R5F, ARM DDI 0460C: "...Modes other than User mode are collectively known as Privileged modes"

Can you give me a hint what is probably the reason for the fault/exception ?

Much thanks in advance for your support.

Tai-Phan

  • 0
    TI__Mastermind 29198 points

    Hi Tai-Phan,

    Tai-Phan Vuong said:
    Based to an example for the LaunchPad AM243x I currently try to rebuild the FreeRTOS library and face with an exception which I really don´t understan

    I don't see anything wrong with what shared. The code is clearing the CPSR.I bit to enable IRQs.

    It appears the processor is in ARM state instead of Thumb state. However, in the SDK I see the FreeRTOS kernel is compiled in Thumb mode. Did you make this modification?

    Can you share any more details about what you did before getting this error?

    Which example are you modifying? How are you modifying it? How are you rebuilding the FreeRTOS kernel library?

    Regards,
    Frank

  • 0 in reply to Frank Livingston
    Prodigy 40 points

    Hi Frank,

    firstable much thanks for your reply.

    Sure I can tell you what I tried to do...currently I try to setup an alternative toolchain with IAR EW (V9.20.4) and Lauterbach Debugger (V2.5.14) based to the empty project with FreeRTOS for R5FSS0, I added the blinking LED funtionality and a timer with toggling an output.

    Based to the make-files: 

    1. ..\source\board\makefile.am243x.r5f.ti-arm-clang

    2. ..\source\drivers\makefile.am243x.r5f.ti-arm-clang

    3. ..\source\kernel\freertos\makefile.am243x.r5f.ti-arm-clang

    I setup IAR library projects for the above mentioned libraries. With IAR created Board Lib and Driver Lib, an some adaptations for IAR and startup it seems to work with the freeRTOS Lib come with the empty project (freertos.am243x.r5f.ti-arm-clang.debug.lib).

    For the last step I would like to create the FreeRTOS Lib with IAR, and face with the fault "undefined instruction" exception.

    You mentioned about arm state and thumb state, i just check check the IAR settings:    

    Hoped to have answered your questions.

    Much thanks in advance for your support.

    If you need the whole project, pls. just tell me, I could send it to you.

  • 0 in reply to Tai-Phan Vuong
    Prodigy 40 points

    Hi Frank,

    firstable much thanks for your reply.

    Sure I can tell you what I tried to do...currently I try to setup an alternative toolchain with IAR EW (V9.20.4) and Lauterbach Debugger (V2.5.14) based to the empty project with FreeRTOS for R5FSS0, I added the blinking LED funtionality and a timer with toggling an output.

    Based to the make-files: 

    1. ..\source\board\makefile.am243x.r5f.ti-arm-clang

    2. ..\source\drivers\makefile.am243x.r5f.ti-arm-clang

    3. ..\source\kernel\freertos\makefile.am243x.r5f.ti-arm-clang

    I setup IAR library projects for the above mentioned libraries. With IAR created Board Lib and Driver Lib, an some adaptations for IAR and startup it seems to work with the freeRTOS Lib come with the empty project (freertos.am243x.r5f.ti-arm-clang.debug.lib).

    For the last step I would like to create the FreeRTOS Lib with IAR, and face with the fault "undefined instruction" exception.

    You mentioned about arm state and thumb state, i just check check the IAR settings:    

    Hoped to have answered your questions.

    Much thanks in advance for your support.

    If you need the whole project, pls. just tell me, I could send it to you.

    +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

    Hi Frank,

    in the meantime I think I have found out what the reason most probably is:

    it is NOT the the assembler instruction "msr cpsr, r12" which causes the exception, BUT it is what this assembler instruction effects: ==> enable IRQs 

    Currently the assembler function HwiP_enable() is invoked in the function Dpl_init() after ClockP_init():

    I made a try and put the HwiP_enable() before starting the system timer with the function ClockP_init(): 

    I could step through the HwiP_enable() without exception, the mentioned exception is only occurred after the systen timer is started.

    There is only 1 ISR used by the FreeRTOS right ?! The system timer ISR ?!

    Hopefully I can find the fault easily if it is only 1 ISR.

    By the way, I would like to ask you, do you have IAR Projects for FreeRTOS, Board and Driver for the Launchpad LP-AM243x which you can provide ?

    Thanks.

  • 0 in reply to Tai-Phan Vuong
    TI__Mastermind 29198 points

    Hi Tai-Phan,

    Tai-Phan Vuong said:
    an some adaptations for IAR and startup

    I would be cautious making changes to the startup code. Changes to startup routines could easily cause the type of issues you've observing.

    Tai-Phan Vuong said:
    I could step through the HwiP_enable() without exception, the mentioned exception is only occurred after the systen timer is started.

    Ok, I gather you believe the exception is caused in the timer ISR code.

    Tai-Phan Vuong said:
    There is only 1 ISR used by the FreeRTOS right ?! The system timer ISR ?!

    Correct, I suggest placing a breakpoint in the ISR and stepping through from that point.

    Tai-Phan Vuong said:
    By the way, I would like to ask you, do you have IAR Projects for FreeRTOS, Board and Driver for the Launchpad LP-AM243x which you can provide ?

    There is currently no plan to provide IAR content with the SDK. Please see the AM243x build sheet here: https://www.ti.com/lit/zip/sprcaj9.

    Regards,
    Frank

  • +1 in reply to Tai-Phan Vuong
    TI__Mastermind 29198 points

    Hi Tai-Phan,

    A few more questions for you:

    • How are handling Sysconfig in your port?
    • Are you using the auto-generated code in your build?
    • Have you enabled the System tick timer in your code?

    Thanks and regards,
    Frank

  • 0 in reply to Frank Livingston
    Prodigy 40 points

    Hi Frank,

    thanks for your answers/comments, I appreciate that very much. And thanks for the AM243x build sheet.

    I have found the cause for the exception after placing some breakpoints in Timer ISR and other functions: 

    Original: 

    void __attribute__((section(".text.hwi"))) HwiP_irq_handler_c(void)

    Note: This function is NOT an IRQ, with the attribute keyword it is just put in a specific section: .text.hwi

    My change which causes the exception:

    __irq __arm void HwiP_irq_handler_c(void)

    I overlooked that it is NOT an IRQ and put the IAR keywords: __irq __arm  

    This is the reason for the exception.

    Your questions:

    • How are handling Sysconfig in your port?

    Do you mean the FreeRTOS Config (FreeRTOSConfig.h), ../freertos\portable\TI_ARM_CLANG\ARM_CR5F 

    I don´t change anything here, just adapt some keywords for IAR like: #define __asm__   __asm 

    • Are you using the auto-generated code in your build?

    Sofar I just convert the CCS-project based to the FreeRTOS empty project to an IAR project and use all source generated by syscfg

    • Have you enabled the System tick timer in your code?

    Yes, this is done by the FreeRTOS Lib: ClockP_init(). As I mentioned I don´t change anything in FreeRTOS empty project for the first, I just want to convert it to an IAR project. As template the for settings of IAR project I use the make file e. g. makefile.am243x.r5f.ti-arm-clang for FreeRTOS Lib.

    What is your intention with your questions? Do you think I have to look at something closely?!

    Thanks in advance for any hints.

     Best regards,

    Tai-Phan

  • 0 in reply to Tai-Phan Vuong
    TI__Mastermind 29198 points

    Hi Tai-Phan,

    Tai-Phan Vuong said:
    This is the reason for the exception.

    I'm glad you were able to resolve the issue.

    Tai-Phan Vuong said:
    Do you mean the FreeRTOS Config (FreeRTOSConfig.h), ../freertos\portable\TI_ARM_CLANG\ARM_CR5F 

    No, I was asking about the application-level code generated by Sysconfig.

    Tai-Phan Vuong said:
    Sofar I just convert the CCS-project based to the FreeRTOS empty project to an IAR project and use all source generated by syscfg

    Ok, understood.

    Tai-Phan Vuong said:
    What is your intention with your questions? Do you think I have to look at something closely?!

    I was just trying to help diagnose the issue.

    Regards,
    Frank